The neck of a bottle has many critical and exacting dimensions. So understanding a bottle’s neck finish is an important step in proper closure/bottle sourcing. Below the various neck finish dimensions are explained.
In cosmetic packaging industry, the terms that are used to designate the size of a cap are the same terms that are used to indicate the neck finish of a bottle, it makes sense, as caps and bottles must fit together perfectly so as not to allow any of the contents of the bottle to escape and not to allow any outside substances to enter the bottle.
Cap sizes and neck finishes are expressed as two numbers. The first number indicates the diameter. For caps, this number represents the inside diameter of the cap. For the neck finish, this number represents the outside diameter of the threads on the neck of the bottle. As can be seen in the example to the right, the dashed red line indicates the inside diameter of the cap as well as the outside diameter of the threads on the neck of the bottle. In this example, the number for both is 24.
The second number refers to the thread finish style. The most common numbers are -400 (one full turn of thread) and 410 (one and a half turns). The common thread finish styles are shown in the image below. Each style is designated by a number. The differences among thread finish styles are the number of thread turns and height of the neck finish.
By now we've learned that those confusing numbers can be found value. Don't panic next time you realize you don't have enough lids to cover your bottles, we (along with the help of a ruler) can help.
If you have any questions regarding neck finishes or products, please reach out to us here!